Concave insert



FIG. 1 is a perspective view of a concave insert showing an embodiment of our new design;

FIG. 2 is a sectional view thereof;

FIG. 3 is a front perspective view of a second embodiment of a concave insert; and,

FIG. 4 is another sectional view thereof.

Only the shapes and portions bounded by solid lines form the claimed design. The elements depicted in dashed lines are shown for illustrative purpose of environment and form no part of the ornamental design. 

CLAIM We claim the ornamental design for the concave insert, as shown and described. 